Nearly all governors depend for their action on centrifugal force and consist of a pair of masses rotating about a spindle driven by the prime mover and kept from flying outward by a controlling force, usually applied by springs. With an increase in speed, the controlling force is overcome and the masses move outward; the movement of the masses is transmitted to valves supplying the prime mover with its working fluid or fuel. The Figure--> shows the conical pendulum governor, invented by James Watt for controlling steam engines. The revolving masses are balls attached to a vertical spindle by link arms, and the controlling force consists of the weight of the balls. If the load on the engine decreases, the speed will increase, the balls M will move out, and the member C will slide up the vertical spindle and reduce the steam admitted to the engine, thus reducing the speed. An increase in the load will have the opposite effect. Modern governors are used to regulate the flow of gasoline to internal-combustion engines and the flow of steam, water, or gas to various types of turbines. Compare flywheel.